At present, the display panel as a display component of an electronic apparatus has been widely used in various electronic products, and a backlight module is one important component in a liquid crystal display device. As for a high-end display panel (LCD or OLED), an array substrate usually adopts an LTPS (low-temperature polycrystalline silicon) to form a TFT (thin film transistor). The commonly used manufacturing method of the low-temperature polycrystalline silicon is melting and recrystallizing an amorphous silicon deposited on a substrate through Excimer Laser Anneal (ELA), the polycrystalline silicon formed by a recrystallization manner using ELA has a large amount of grain boundaries, as a surface appearance shown in FIG. 1, the large amount of grain boundaries may be distributed disorderly in the finally formed channel of the TFT, and these grain boundaries may form a defect state center and affect output characteristics of the TFT.